The present invention generally relates to insert recording systems for inserting and recording a new arbitrary video signal within an arbitrary section of recorded tracks among a group of video signal tracks recorded on a magnetic tape, and more particularly to an insert recording system capable of performing insert recording with a simple construction so that disturbance is not introduced in a reproduced picture at a joint between an insert recording part and a recorded track part, and so that a stable reproduced picture of high quality can be obtained.
Generally, in a recording and reproducing apparatus of the so-called helical scanning system, a video signal is recorded on a magnetic tape by one or a plurality of rotary video heads on tracks which are obliquely formed with respect to the longitudinal direction of the magnetic tape. One field of the video signal, for example, is recorded on each of the oblique tracks. When electronically editing to insert and record a new and separate video signal, instead of the recorded video signal, at an arbitrary part of the recorded magnetic tape recorded with the video signal, the recorded video track part which is to be subjected to the insert recording is normally erased before the new and separate video signal is inserted and recorded by the rotary video head.
There is a conventional system in which the erasure of the recorded video track upon insert recording is performed by a full-width erasing head. However, in this system, the full-width erasing head erases all the tracks along the width direction of the magnetic tape. Thus, the control track and the audio track were also erased instead of only erasing the video tracks which are to be erased. Accordingly, in this conventional system which uses the full-width erasing head, a control signal must be recorded onto the control track when inserting and recording the new video signal onto the erased part of the magnetic tape. But when a magnetic tape subjected to such insert recording is reproduced, the period of the control signal does not assume a predetermined constant value at the joint between the insert recording part and the recorded track part. Hence, the operation of a servo circuit which is supplied with the reproduced control signal becomes unstable at the above joint, and there is a disadvantage in that disturbance is easily introduced in the reproduced picture at the above joint.
In order to overcome the disadvantages of the above conventional system, another system was proposed in which only the video tracks to be erased are erased by a so-called flying erase head, and the new video signal is thereafter inserted and recorded onto the erased part of the magnetic tape. The above flying erase head is fixed to a rotary body such as a rotary drum onto which the rotary video head is fixed, at a position leading the rotary video head, and is a rotary head exclusively for erasure. However, in this system, because it is necessary to provide the flying erase head at a position leading the recording and reproducing rotary video head, the same number of flying erase heads is required as the number of,video heads. Accordingly, the manufacturing cost increases, and the mechanical head mounting process to accurately adjust the mutual positional relationship of each head must be performed with exceedingly high accuracy. Therefore, such a system was not suited for a general recording and reproducing apparatus for home use, where there is a demand to keep the cost down to a minumum.
Furthermore, in another conventional insert recording system, the new video signal is recorded onto the recorded video track by the rotary video head according to a so-called overlap recording. In this system, the recorded video signal is erased due to the biasing effect, and the new video signal is simultaneously recorded with the erasure. According to this system, the cost of the apparatus is reduced since it is not necessary to provide a head exclusively for erasure, and moreover, disturbance is not introduced in the reproduced picture at the joint between the insert recording part and the recorded video track part because only the video track is subjected to simultaneous erasure and recording. However, in this system, the recorded video signal is erased by recording the new video signal onto the recorded video track. Therefore, there is a disadvantage in that the quality of the reproduced picture is poor at the insert recording track part.